I seem to have veins that protrude in my legs. Why does that happen?

See Vein Specialist. Varicose veins are bulging grape-like appearing veins which are most commonly seen on the legs. These are due to leaking(refluxing) valves usually in the saphenous system. Some causes include hereditary, pregnancy, trauma and aging. The gold standard of treatment is to have a venous reflux ultrasound to both diagnose and form a treatment plan. You should see a vein specialist.